The mouth of Boulder Canyon -- just 12 hours earlier filled with roiling, churning floodwaters -- was a slightly calmer scene Friday, though it prominently bore the wounds of the historic assault by a waterway not quite done flexing its muscle.

Three-to-four feet of mud covered a once-passable road, ditches that rarely run a trickle spilled a frothy brown stew into Eben G. Fine Park and Boulder Creek beyond it, and part of an office park tucked away at the west end of Arapahoe Avenue collapsed to the ground.

Greg Naber, a Farmers Insurance agent whose building at 190 Arapahoe Ave. took on a wall of mud from an upslope slide that shattered his picture window and submerged his office, thought the worst already was behind him when he left for home Thursday night.

"I left here at 6 last night and everything was fine," he said Friday as a team of mud-splattered helpers shoveled muck from his corner office. "Then this morning, I turned the corner and I was in shock at how much debris there was in the road."

And at the amount of debris outside his office window. A massive boulder had been pushed downhill by a torrent of water, coming to a rest mere feet from the corner of Naber's building.

"Think of the power that moved that rock downhill," he said. "This is surreal. It's unimaginable the volume of water that came through here."

Naber fared better than his next door neighbor -- the Canyonside Office Park at 100 Arapahoe Ave. A mustard-orange building lay crumpled on the ground Friday while the bottom half of a twin structure was buckled out, partially torn from its foundations. Part of a computer case lay strewn among flattened vegetation while a self-help book on pre-parenting from conception made for an odd sight laying quietly on the battered hillside.

'Pretty remarkable'

Boulder Mayor Matt Appelbaum, who was touring the mouth of the canyon Friday afternoon with the city's transportation and utilities maintenance manager, Felix Gallo, looked at the collapsed building in disbelief.

"This is pretty remarkable," he said. "It's the only place in the city I've seen with this much non-road structural damage."

But he said the overall hit Boulder took from the multi-day storm was tremendous, with damage to city buildings, a "significant" number of flooded residential basements and millions of dollars of damage to roads and other infrastructure.

Appelbaum said he was on the phone with U.S. Sen. Mark Udall, D-Colo., Friday morning and with officials from the White House's office of intergovernmental affairs to talk about possible federal and state aid for Boulder and Boulder County. President Barack Obama signed an emergency order Thursday approving federal disaster aid for the county.

While specific aid amounts will be determined in the future, the mayor said Boulder has so far done a good job of putting in place flood mitigation measures on streets and underpasses throughout the city.

"There's no question it would have been worse if we hadn't taken these actions," Appelbaum said.

In the end, the rain came too fast and too hard -- nearly 15 inches since the storm's beginning on Monday -- for even the best designed municipal water works system to handle, he said.

"You can't design your entire sewer storm system for 100-year or greater events," Appelbaum said. "I don't think it's feasible or something you'd have the funding to do. This was so big and so widespread -- it was just going to overwhelm the infrastructure you have in place."

But once the damage assessment has been completed, he said, it will be instructive to see how accurately the city's flood maps reflect real damage on the ground and help determine whether they need to be redrawn or not.

Breaking down doors

A little further west along Arapahoe Avenue, the 68-year-old Silver Saddle Motel took on water and mud Thursday night and Friday morning.

Ameer Qalbani, a University of Colorado graduate student working on his MBA, ventured out to survey the damage with friends, and the motel's owner invited him to take a look inside. He took photos and videos of cabins with waterlines several feet high. There were gashes in some of the doors where management had created holes to let the water out.

"They had these cabins, which were totally full of water, up to halfway up and they had to break the doors in to get the water out," Qalbani said. "(There were) five or six inches of mud."

When a reporter asked the owners of Silver Saddle Motel if they wanted to talk about weathering the storm of the century, they declined to comment.

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